scholarly journals Sonoelectrochemical synthesis of silver nanoparticles in polyvinylpyrrolidone solutions

2021 ◽  
Vol 4 (1) ◽  
pp. 82-87
Author(s):  
M. V. Shepida ◽  
◽  
M. A. Sozanskyi ◽  
Yu. V. Sukhatskiy ◽  
A. S. Mazur ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Formation Rate ◽  
Ultrasonic Field ◽  
Colloidal Solutions ◽  
Complex Ions ◽  
Diffusion Kinetic ◽  
Wide Range ◽  
Sonoelectrochemical Synthesis ◽  
The Stability ◽  
Sonochemical Reduction

The results of investigations of the influence of main parameters (surfactant concentration and temperature) on the synthesis of silver nanoparticles (AgNPs) by the sonoelectrochemical method in polyvinylpyrrolidone (PVP) solutions by cyclic voltammetry (CVA) are presented. It is shown that the ultrasonic field (22 kHz) leads to an increase in the anodic and cathodic currents by ~30 %. A scheme of the AgNPs formation has been proposed, which includes the following main processes: 1) dissolution of sacrificial silver anodes at E = 0.2...1.0 V with the formation of [AgPVP]+ complex ions; 2) cathodic and sonochemical reduction of the latter to Ag(0); 3) formation of AgNPs. It has been established that with an increase in PVP concentration from 1 to 4 g·L-1, the anodic and cathodic currents decrease by 40–60 %. The formation rate of AgNPs also decreases. The growth of anodic and cathodic currents and the formation rate of nanoparticles in the range of 20…60 °C corresponds to the diffusion-kinetic action of the temperature factor. The CVA curves practically do not change in time, which indicates the stability of anodic and cathodic processes at prolonged sonoelectrochemical synthesis. The character of the UV-Vis spectra of AgNPs colloidal solutions in PVP with the 405…410 nm absorption maximum is the same in a wide range of nanoparticle concentrations.

scholarly journals Sonoelectrochemical Synthesis of Antibacterial Active Silver Nanoparticles in Rhamnolipid Solution

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Mariana Shepida ◽  
Orest Kuntyi ◽  
Martyn Sozanskyi ◽  
Yuriy Sukhatskiy
Keyword(s):  
Cyclic Voltammetry ◽  
Absorption Maximum ◽  
Colloidal Solutions ◽  
Diffusion Kinetic ◽  
Ultrasound Field ◽  
Wide Range ◽  
Sonoelectrochemical Synthesis ◽  
Cathodic Processes ◽  
The Stability ◽  
And Staphylococcus Aureus

The results of studies of the synthesis of AgNPs colloidal solutions by cyclic voltammetry (E from +1.0 to −1.0 V) in rhamnolipid (RL) solutions and the use of soluble anodes in the ultrasound field (22 kHz) are presented. It is shown that the algorithm of anodic dissolution—reduction of Ag(I)—nucleation, and formation of AgNPs makes it possible to obtain nanoparticles with the size from 1 nm to 3 nm. It was found that with an increase in the RL concentration from 1 g/L to 4 g/L, the anodic and cathodic currents increase as well as the rate of AgNPs formation, respectively. The rate of nanoparticles formation also increases with an increase in temperature from 20°C to 60°C, and it corresponds to the diffusion-kinetic range of action of this factor. Moreover, the size of AgNPs depends little on the temperature. The character of the UV-Vis pattern of AgNPs colloidal solutions in RL (with an absorption maximum of 415 nm) is the same over a wide range of nanoparticle concentrations. The curves practically do not change in time, which indicate the stability of anodic and cathodic processes during prolonged sonoelectrochemical synthesis. The cyclic voltammetry curves practically do not change in time, which indicate the stability of anodic and cathodic processes during prolonged sonoelectrochemical synthesis. The antimicrobial activity of synthesized AgNPs solutions to strains of Escherichia coli, Candida albicans, and Staphylococcus aureus was established.

scholarly journals Sonoelectrochemical Synthesis of Silver Nanoparticles in Sodium Polyacrylate Solution

2021 ◽  
Vol 11 (4) ◽  
pp. 12202-12214
Keyword(s):  
Silver Nanoparticles ◽  
Nanoparticle Synthesis ◽  
Ultrasonic Field ◽  
Sodium Polyacrylate ◽  
Silver Colloids ◽  
High Antibacterial Activity ◽  
Vis Spectroscopy ◽  
Sonoelectrochemical Synthesis ◽  
The Stability ◽  
Increasing Temperature

The paper shows the effectiveness of a “green” synthesis of silver nanoparticles (AgNPs) in sodium polyacrylate (NaPA) solutions by sonoelectrochemical method using silver sacrificial anodes. Using the cyclic voltammetry in the ultrasonic field in the range of E from 1.0 to -1.0 V, the temperature and NaPA concentration are the main parameters influencing the rate of synthesis and the size of AgNPs. As these parameters increase, the rate of nanoparticle synthesis increases. According to TEM studies, with increasing temperature and decreasing NaPA concentration, there is a tendency to increase the size of AgNPs. However, in all of the cases, the size of AgNPs does not exceed 30 nm. Using the UV–Vis spectroscopy, it was found that the position of the absorption peak at c.a. 500 nm, corresponding to the silver nanoparticles, is practically not shifted during numerous cycles. This fact may indicate the stability of sonoelectrochemical synthesis of AgNPs in time. Synthesized AgNPs revealed high antibacterial activity against gram-positive and gram-negative strains of typical pathogens of nosocomial infections, demonstrating the prospect of using sonoelectrochemical technique for obtaining silver colloids as a component of bactericidal drugs.

scholarly journals Reactivity and Chemical Sintering of Carey Lea Silver Nanoparticles

Nanomaterials ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1525
Author(s):  
Sergey Vorobyev ◽  
Elena Vishnyakova ◽  
Maxim Likhatski ◽  
Alexander Romanchenko ◽  
Ivan Nemtsev ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Silver Nanoparticles ◽  
Flexible Electronics ◽  
Photoelectron Spectroscopy ◽  
Colloidal Solutions ◽  
Ag Nps ◽  
Wide Range ◽  
Carboxylic Groups ◽  
The Media ◽  
Sulfide Ions

Carey Lea silver hydrosol is a rare example of very concentrated colloidal solutions produced with citrate as only protective ligands, and prospective for a wide range of applications, whose properties have been insufficiently studied up to now. Herein, the reactivity of the immobilized silver nanoparticles toward oxidation, sulfidation, and sintering upon their interaction with hydrogen peroxide, sulfide ions, and chlorocomplexes of Au(III), Pd(II), and Pt(IV) was investigated using SEM and X-ray photoelectron spectroscopy (XPS). The reactions decreased the number of carboxylic groups of the citrate-derived capping and promoted coalescence of 7 nm Ag NPs into about 40 nm ones, excluding the interaction with hydrogen peroxide. The increased nanoparticles form loose submicrometer aggregates in the case of sulfide treatment, raspberry-like micrometer porous particles in the media containing Pd(II) chloride, and densely sintered particles in the reaction with inert H2PtCl6 complexes, probably via the formation of surface Ag-Pt alloys. The exposure of Ag NPs to HAuCl4 solution produced compact Ag films along with nanocrystals of Au metal and minor Ag and AgCl. The results are promising for chemical ambient temperature sintering and rendering silver-based nanomaterials, for example, for flexible electronics, catalysis, and other applications.

scholarly journals Coating-Dependent Effects of Silver Nanoparticles on Tobacco Seed Germination and Early Growth

2020 ◽  
Vol 21 (10) ◽  
pp. 3441 ◽  
Author(s):  
Renata Biba ◽  
Dajana Matić ◽  
Daniel Mark Lyons ◽  
Petra Peharec Štefanić ◽  
Petra Cvjetko ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Growth Parameters ◽  
Antimicrobial Properties ◽  
Chemical Properties ◽  
Early Growth ◽  
Consumer Products ◽  
Negative Effects ◽  
Wide Range ◽  
Living Organisms ◽  
The Stability

Silver nanoparticles (AgNPs) are used in a wide range of consumer products because of their excellent antimicrobial properties. AgNPs released into the environment are prone to transformations such as aggregation, oxidation, or dissolution so they are often stabilised by coatings that affect their physico-chemical properties and change their effect on living organisms. In this study we investigated the stability of polyvinylpyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB) coated AgNPs in an exposure medium, as well as their effect on tobacco germination and early growth. AgNP-CTAB was found to be more stable in the solid Murashige and Skoog (MS) medium compared to AgNP-PVP. The uptake and accumulation of silver in seedlings was equally efficient after exposure to both types of AgNPs. However, AgNP-PVP induced only mild toxicity on seedlings growth, while AgNP-CTAB caused severe negative effects on all parameters, even compared to AgNO3. Moreover, CTAB coating itself exerted negative effects on growth. Cysteine addition generally alleviated AgNP-PVP-induced negative effects, while it failed to improve germination and growth parameters after exposure to AgNP-CTAB. These results suggest that the toxic effects of AgNP-PVP are mainly a consequence of release of Ag+ ions, while phytotoxicity of AgNP-CTAB can rather be ascribed to surface coating itself.

Performance of Electronic Structure Methods for the Description of Hückel-Möbius Interconversions in Extended π-Systems

2019 ◽  
Author(s):  
Tatiana Woller ◽  
Ambar Banerjee ◽  
Nitai Sylvetsky ◽  
Xavier Deraet ◽  
Frank De Proft ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Basis Set ◽  
Dft Methods ◽  
Molecular Switching ◽  
Wide Range ◽  
Electronic Structure Methods ◽  
Explicitly Correlated ◽  
Relative Errors ◽  
The Stability ◽  
Basis Set Expansion

<p>Expanded porphyrins provide a versatile route to molecular switching devices due to their ability to shift between several π-conjugation topologies encoding distinct properties. Taking into account its size and huge conformational flexibility, DFT remains the workhorse for modeling such extended macrocycles. Nevertheless, the stability of Hückel and Möbius conformers depends on a complex interplay of different factors, such as hydrogen bonding, p···p stacking, steric effects, ring strain and electron delocalization. As a consequence, the selection of an exchange-correlation functional for describing the energy profile of topological switches is very difficult. For these reasons, we have examined the performance of a variety of wavefunction methods and density functionals for describing the thermochemistry and kinetics of topology interconversions across a wide range of macrocycles. Especially for hexa- and heptaphyrins, the Möbius structures have a pronouncedly stronger degree of static correlation than the Hückel and figure-eight structures, and as a result the relative energies of singly-twisted structures are a challenging test for electronic structure methods. Comparison of limited orbital space full CI calculations with CCSD(T) calculations within the same active spaces shows that post-CCSD(T) correlation contributions to relative energies are very minor. At the same time, relative energies are weakly sensitive to further basis set expansion, as proven by the minor energy differences between MP2/cc-pVDZ and explicitly correlated MP2-F12/cc-pVDZ-F12 calculations. Hence, our CCSD(T) reference values are reasonably well-converged in both 1-particle and n-particle spaces. While conventional MP2 and MP3 yield very poor results, SCS-MP2 and particularly SOS-MP2 and SCS-MP3 agree to better than 1 kcal mol<sup>-1</sup> with the CCSD(T) relative energies. Regarding DFT methods, only M06-2X provides relative errors close to chemical accuracy with a RMSD of 1.2 kcal mol<sup>-1</sup>. While the original DSD-PBEP86 double hybrid performs fairly poorly for these extended p-systems, the errors drop down to 2 kcal mol<sup>-1</sup> for the revised revDSD-PBEP86-NL, again showing that same-spin MP2-like correlation has a detrimental impact on performance like the SOS-MP2 results. </p>

Antimicrobial Activity of Silver Nanoparticles Prepared Under an Ultrasonic Field

2011 ◽  
Vol 4 (3) ◽  
pp. 1491-1496
Author(s):  
Umadevi M ◽  
Rani T ◽  
Balakrishnan T ◽  
Ramanibai R
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Activity ◽  
Silver Nanoparticles ◽  
Reduction Method ◽  
Therapeutic Potential ◽  
Chemical Reduction ◽  
Ultrasonic Field ◽  
Great Promise ◽  
Chemical Reduction Method ◽  
E Coli

Nanotechnology has great promise for improving the therapeutic potential of medicinal molecules and related agents. In this study, silver nanoparticles of different sizes were synthesized in an ultrasonic field using the chemical reduction method with sodium borohydride as a reducing agent. The size effect of silver nanoparticles on antimicrobial activity were tested against the microorganisms Staphylococcus aureus (MTCC No. 96), Bacillus subtilis (MTCC No. 441), Streptococcus mutans (MTCC No. 497), Escherichia coli (MTCC No. 739) and Pseudomonas aeruginosa (MTCC No. 1934). The results shows that B. subtilis, and E. coli were more sensitive to silver nanoparticles and its size, indicating the superior antimicrobial efficacy of silver nanoparticles. 

Insights into Potent Therapeutical Antileukemic Agent L-glutaminase Enzyme Under Solid-state Fermentation: A Review

2020 ◽  
Vol 21 (3) ◽  
pp. 211-220 ◽  
Author(s):  
Chandrasai Potla Durthi ◽  
Madhuri Pola ◽  
Satish Babu Rajulapati ◽  
Anand Kishore Kola
Keyword(s):  
Solid State ◽  
Solid State Fermentation ◽  
Food Industry ◽  
Energy Requirement ◽  
Production Studies ◽  
Wide Range ◽  
Hybridoma Technology ◽  
Bacteria And Fungi ◽  
The Stability ◽  
Glutaminase Activity

Aim & objective: To review the applications and production studies of reported antileukemic drug L-glutaminase under Solid-state Fermentation (SSF). Overview: An amidohydrolase that gained economic importance because of its wide range of applications in the pharmaceutical industry, as well as the food industry, is L-glutaminase. The medical applications utilized it as an anti-tumor agent as well as an antiretroviral agent. L-glutaminase is employed in the food industry as an acrylamide degradation agent, as a flavor enhancer and for the synthesis of theanine. Another application includes its use in hybridoma technology as a biosensing agent. Because of its diverse applications, scientists are now focusing on enhancing the production and optimization of L-glutaminase from various sources by both Solid-state Fermentation (SSF) and submerged fermentation studies. Of both types of fermentation processes, SSF has gained importance because of its minimal cost and energy requirement. L-glutaminase can be produced by SSF from both bacteria and fungi. Single-factor studies, as well as multi-level optimization studies, were employed to enhance L-glutaminase production. It was concluded that L-glutaminase activity achieved by SSF was 1690 U/g using wheat bran and Bengal gram husk by applying feed-forward artificial neural network and genetic algorithm. The highest L-glutaminase activity achieved under SSF was 3300 U/gds from Bacillus sp., by mixture design. Purification and kinetics studies were also reported to find the molecular weight as well as the stability of L-glutaminase. Conclusion: The current review is focused on the production of L-glutaminase by SSF from both bacteria and fungi. It was concluded from reported literature that optimization studies enhanced L-glutaminase production. Researchers have also confirmed antileukemic and anti-tumor properties of the purified L-glutaminase on various cell lines.

scholarly journals A preliminary investigation of the conditions which determine the stability of irreversible hydrosols

1900 ◽  
Vol 66 (424-433) ◽  
pp. 110-125 ◽  
Keyword(s):  
Slow Rate ◽  
Preliminary Investigation ◽  
Colloidal Solutions ◽  
Solid Matter ◽  
The Stability

It has long been held that a large number of colloidal solutions are related to or identical with suspensions of solid matter in a fluid in which the particles of solid are so small as to settle at an infinitely slow rate. Such solutions are the colloidal solutions of metals and of sulphides such as those of antimony, arsenic, and cadmium.

scholarly journals Mapping large-scale-structure evolution over cosmic times

2021 ◽  
Author(s):  
Marta B. Silva ◽  
Ely D. Kovetz ◽  
Garrett K. Keating ◽  
Azadeh Moradinezhad Dizgah ◽  
Matthieu Bethermin ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
High Redshift ◽  
Formation Rate ◽  
Far Infrared ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Structure Evolution ◽  
Intensity Mapping ◽  
Wide Range

AbstractThis paper outlines the science case for line-intensity mapping with a space-borne instrument targeting the sub-millimeter (microwaves) to the far-infrared (FIR) wavelength range. Our goal is to observe and characterize the large-scale structure in the Universe from present times to the high redshift Epoch of Reionization. This is essential to constrain the cosmology of our Universe and form a better understanding of various mechanisms that drive galaxy formation and evolution. The proposed frequency range would make it possible to probe important metal cooling lines such as [CII] up to very high redshift as well as a large number of rotational lines of the CO molecule. These can be used to trace molecular gas and dust evolution and constrain the buildup in both the cosmic star formation rate density and the cosmic infrared background (CIB). Moreover, surveys at the highest frequencies will detect FIR lines which are used as diagnostics of galaxies and AGN. Tomography of these lines over a wide redshift range will enable invaluable measurements of the cosmic expansion history at epochs inaccessible to other methods, competitive constraints on the parameters of the standard model of cosmology, and numerous tests of dark matter, dark energy, modified gravity and inflation. To reach these goals, large-scale structure must be mapped over a wide range in frequency to trace its time evolution and the surveyed area needs to be very large to beat cosmic variance. Only a space-borne mission can properly meet these requirements.

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